uio: uio_fsl_elbc_gpcm: use device-managed allocators

uio: uio_fsl_elbc_gpcm: use device-managed allocators

This change moves all the simple allocations to use device-managed
allocator functions. This way their life-time is tied to the
platform_device object, so when this gets free'd these allocations also get
cleaned up.
The final effect is that error & exit paths get cleaned up a bit.

Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Link: https://lore.kernel.org/r/20201119154903.82099-3-alexandru.ardelean@analog.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>